Many patients with coronary artery disease manifest evidence for myocardial ischemia at rest, such as diastolic filling abnormalitites and regional asynchrony, both of which may be reversed after successful percutaneous transluminal coronary angioplasty. Further evidence is the improvement in regional and global ventricular systolic function that occurs after coronary bypass operation. We observed a significant improvement in left ventricular ejection fraction at rest in 28 patients without previous myocardial infarction who were studied by radionuclide angiography before and 6 months after coronary bypass surgery. Moreover, quantitative regional analysis demonstrated improved regional function at rest after operation in those regions developing ischemia during excercise before operation. These data support the concept that may coronary artery disease patients have subclinical left ventricular ischemia under resting conditions which is reversible after restoration of coronary flow.